Radiation durable organic compounds with high transparency in the vaccum ultraviolet, and method for preparing

ABSTRACT

This invention concerns radiation durable organic compositions which are well-suited for use in 157 nm lithography by virtue of their high transparency and excellent radiation durability, and to a process for the preparation thereof.

FIELD OF THE INVENTION

This invention is directed to the development of materials suitable foruse in the fabrication of shaped articles by photolithographictechniques, more specifically to the fabrication of circuits byphotolithography in the region of the electromagnetic spectrum known asthe vacuum ultraviolet. Most specifically, this invention is directed tophotolithography at wavelengths below 260 nm, particularly at 157 nm and193 nm. In particular, this invention is directed to new organiccompositions which are particularly well-suited for use in vacuumultraviolet photolithography by virtue of their high transparency andexcellent photochemical stability, and to a process for the preparationthereof.

TECHNICAL BACKGROUND OF THE INVENTION

As the electronics industry moves to adapt the methods ofphotolithography to the fabrication of ever-smaller circuit elements,resort is made to ever-smaller wavelengths of light in order to achievethe higher resolution images required.

Photolithographic processes employing wavelengths in the so-called“vacuum ultra-violet” (VUV) are now under development, with considerableattention being focused on 157 nanometer (nm) and 193 nmphotolithography. Vacuum ultraviolet radiation is of sufficiently highenergy to break chemical bonds in some normally stable materialsresulting in the formation of highly reactive free-radicals. It will beappreciated by one of skill in the art that the generation of a smallnumber of free radicals can have catastrophic effects on the chemicalstability of the host material by virtue of a free-radical chainreaction. The role of free-radicals in photochemical degradation ofmaterials is well known. There are many types of free radicals,including hydroxyl radicals, oxygen radicals, and organic radicals.These free radicals are generated when sufficient energy is absorbed bya precursor molecule to cause it to dissociate non-ionically, formingspecies of neutral charge but sporting an unpaired electron.

Titze in Photodissoziation von H ₂ O bei 157 nm, Max Planck Inst.,Gottingen, Germany, 1984, discloses photolysis of water at 157 nm toform hydrogen and hydroxide radicals.

A. C. Fozza, J. E. Klemberg-Sapieha, and M. R. Wertheimer, Plasmas andPolymers, Vol. 4, No 2/3, 1999, pages 183 to 206, discusses oxygen'sundergoing photo-dissociation to activated oxygen atoms at wavelengthsless than 170 nm. Also disclosed are bond breaking reactions that occurin the vacuum ultraviolet with polyethylene, polystyrene, andpolymethymethacrylate. V. N. Vasilets, I. Hirata, H. Iwata, Y. Ikada,Journal of Polymer Science: Part A: Polymer Chemistry, Vol 36, 2215-2222(1998) discusses radical formation and photooxidation whentetrafluoroethylene/hexafluoropropylene copolymer is irradiated with 147nm light:

N. Ichinose and S. Kawanishi, Macromolecules, 1996, 29, 4155-4157discloses the irradiation of polymers such as Teflon® PTFE, Teflon® FEP,Teflon® PFA, Tefzel®, and polyvinylidene fluoride with light at 185,193, 248, and 254 nm. When the polymer surface was in contact withnitrogen-purged water, extensive surface reaction was detected. Thesurface reactivity was particularly apparent at 185, 193, and 248 nm butmuch less so if at all at 254 nm. Perfluorinated polymers such asTeflon® PTFE and Teflon® PFA reacted more readily than partiallyfluorinated polymers such as Tefzel® and polyvinylidene fluoride. Nosignificant photochemistry was observed in the absence of water.Saturation of the water with oxygen also completely inhibited thesurface chemistry. It is further taught that water starts to absorbaround 190 to 200 nm and that photons of wavelengths shorter than191-207 nm have sufficient energy to exceed the threshold ionizationenergy of liquid water.

It is very well-known in the art that oxygen radicals, which areproduced by numerous means, are highly reactive with a tremendous rangeof materials, causing degradation both in the presence and absence ofwater, depending upon the specific circumstances. Prevention ofoxidation is a large and complex art in itself, with a long history.

Considerable emphasis in the art has been placed on identifying organicpolymeric compositions suitable for use in the VUV. See for example WO0185811 and WO 137044 which disclose fluorinated polymeric compositionshaving high transparency at 157 nm. Considerably less emphasis has beenplaced upon the low molecular weight organic compositions which areemployed as solvents for the polymer during spin coating, asplasticizers for polymeric films, or in an adhesive formulation.Alternatively, an organic fluid or gel may be employed as an immersionmedium in immersion photolithography, as disclosed for example bySwitkes and Rothschild (J. Vac. Sci. Technol. B, 19 (6), 2353-6,November/December 2001) in which a fluid medium is used between theprojection lens of the optical stepper and the photoresist coatedsubstrate (typically a silicon wafer) which will receive and detect thephotolithographic image. But, whether a polymer or a low molecularorganic composition, if the material resides in the light path betweenthe source and the target, the material needs to be transparent anddurable.

For a material to be useful in VUV photolithography it is necessary butnot sufficient that it exhibit high transparency, particularly at 157 nmand 193 nm; it must also exhibit high photochemical stability known inthe art as radiation durability. Radiation durability is the property ofa material to retain transparency upon being subject to exposure toelectromagnetic radiation of a particular frequency. In many aspects ofphotolithography, commercial considerations require a transparentmaterial to retain a high degree of transparency while being subject toa significant cumulative dose of radiation.

Hydrofluorocarbons having the general formula C_(n)F_(2n+2−x)H_(x) arewell known in the art, and are readily prepared by known methods. Onesuch method is the addition of hydrogen across the double bond of afluoroolefin or a hydrofluorocarbon olefin using nickel or palladium asa catalyst as described in M. Hudlicky, Chemistry of Organic FluorineCompounds, 2^(nd) Edition, John Wiley and Sons, New York, 1976 pages 174and 175. In the alternative, said hydrofluorocarbons may be prepared bythe reduction of Br, Cl, and I atoms in fluorocarbons orhydrofluorocarbons to H with inorganic reducing agents such as LiAlH4 orZn as described in Hudlicky, op. cit., page 182 or alternatively on page189. In yet another method, said hydrofluorocarbons may be preparedusing organic reducing agents such as tributyltinhydride as described inHudlicky, op. cit., page 197.

F[CF(CF₃)CF₂O]nCF₂CF₃, is known in the art, as described in, ModernFluoropolymers, J. Scheirs, editior Chapter 24, “Perfluoropolyethers(Synthesis, Characterization, and Applications)” John Wiley & Sons, NewYork, 1997. F[CF(CF₃)CF₂O]_(n)CFHCF₃ where n=1 to 5 comes from anintermediate in the synthesis of F[CF(CF₃)CF₂O]nCF₂CF₃ in which a —COOHend group has been thermolysed to hydrogen rather than converted to —Fwith fluorine gas X—R_(f) ^(a)[OR_(f) ^(b)]nOR_(f) ^(c)Y wherein X and Ycan be hydrogen or fluorine and R_(f) ^(a), R_(f) ^(b), and R_(f) ^(c)are 1 to 3 carbon fluorocarbon radicals, linear or branched is a knownvariation of F[CF(CF₃)CF₂O]nCF₂CF₃, also described in ModernFluorpolymers, op. cit. HCF₂(OCF₂)_(n)(OCF₂CF₂)_(m)OCF₂H where n+m=1to 8is a variation of the synthesis of said X—R_(f) ^(a)[OR_(f) ^(b)]nOR_(f)^(c)Y in which the end groups are not fluorinated but rather diverted toother chemistry as described in Modern Fluoropolymers, op. cit., on p.441 happens to show end groups being reduced to CH2OH rather thanconverted to H). Not all of the variations implied by the genericformulas may be known or easily made: for example Class ii where one hasH[CF(CF₃)CF₂O]_(n)CF₂H.

CF₃CH₂CF₂CH₃ is known to be synthesized by reacting CCl₄ and CH₂═CClCH₃to give CCl₃CH₂CCl₂CH₃, and then replacement of the chlorines bytreatment in hydrofluoric acid. See R. Bertocchio, A. Lantz, L.Wedlinger, Chem. Abstracts 127: 161495.

SUMMARY OF THE INVENTION

The present invention provides for an organic composition comprisingless than 20 parts per million of water, less than 90 ppm of oxygen, andone or more compounds selected from the group consisting of:

-   -   i) cyclic, linear, or branched hydrofluorocarbons having 2 to 10        carbon atoms in which there are more fluorines than hydrogen, no        runs of adjacent C—H bonds longer than two (CH—CH), no runs of        adjacent C—F bonds longer than 6 (CF—CF—CF—CF—CF—CF), and no        —CH₂CH₃ radicals;    -   ii) X—R_(f) ^(a)[OR_(f) ^(b)]nOR_(f) ^(c)Y wherein X and Y can        be hydrogen or fluorine and R_(f) ^(a), R_(f) ^(b), and R_(f)        ^(c) are 1 to 3 carbon fluorocarbon radicals, linear or branched    -   in which there are more fluorines than hydrogens, no runs of        adjacent C—H bonds longer than two are present, no —CH₂CH₃        radicals are present and no sequences with hydrogen on both        sides of an ether oxygen (CH—O—CH) are present;    -   iii) C_(n)F_(2n−v+2)H_(v) wherein n=2 to 10, v<n+1, the number        of fluorines equals or exceeds the number of hydrogens, no runs        of adjacent C—H bonds longer than two are present, no runs of        adjacent C—F bonds longer than 6 are present, and no CH₂CH₃        radicals are present;    -   iv) C_(n)F_(2n+1)CFHCFHC_(m)F_(2m+1) where n equals 1 to 4; and        m equals 1 to 4;    -   v) CF₃CH₂CF₂CH₃;    -   vi) F[CF(CF₃)CF₂O]_(n)CFHCF₃ where n=1 to 5;    -   vii) F[CF(CF₃)CF₂O]_(n)CF₂CF₃ where n=1 to 5;    -   viii) HCF₂(OCF₂)_(n)(OCF₂CF₂)_(m)OCF₂H where n+m=1 to 8; and,    -   ix) cyclic, linear, or branched perfluorocarbon and        hydrofluorocarbon amines, and ether-amines in which there are        more fluorines than hydrogens, no runs of hydrogen longer than        two (CH—CH), no —CH₂CH₃ radicals are present, no runs of        adjacent C—F bonds longer than 6 (CF—CF—CF—CF—CF—CF), and no C—H        bonds immediately adjacent to either nitrogen or oxygen.

The present invention further provides for a process for preparing anorganic composition for use in optical imaging applications the processcomprising subjecting to treatment with one or more means for extractingone or more photochemically active species, a compound selected from thegroup consisting of:

-   -   i) cyclic, linear, or branched hydrofluorocarbons having 2 to 10        carbon atoms in which there are more fluorines than hydrogen, no        runs of adjacent OH bonds longer than two (CH—CH), no runs of        adjacent C—F bonds longer than 6 (CF—CF—CF—CF—CF—CF), and no        —CH₂CH₃ radicals;    -   ii) X—R_(f) ^(a)[OR_(f) ^(b)]nOR_(f) ^(c)Y wherein X and Y can        be hydrogen or fluorine and R_(f) ^(a), R_(f) ^(b), and R_(f)        ^(c) are 1 to 3 carbon fluorocarbon radicals, linear or branched    -   in which them are more-fluorines than hydrogens, no runs of        adjacent C—H bonds longer than two are present, no —CH₂CH₃        radicals are present and no sequences with hydrogen on both        sides of an ether oxygen (CH—O—CH) are present;    -   iii) C_(n)F_(2n−v+2)H_(v) wherein n=2 to 10, v<n+1, no runs of        adjacent C—H bonds longer than two are present, no runs of        adjacent C—F bonds longer than 6 are present, and no CH₂CH₃        radicals are present;    -   iv) C_(n)F_(2n+1)CFHCFHC_(m)F_(2m+1) where n equals 1 to 4; and        m equals 1 to 4;    -   v) CF₃CH₂CF₂CH₃;    -   vi) F[CF(CF₃)CF₂O]_(n)CFHCF₃ where n=1 to 5;    -   vii) F[CF(CF₃)CF₂O]_(n)CF₂CF₃ where n=1 to 5;    -   viii) HF₂(OCF₂)_(n)(OCF₂CF₂)_(m)OCF₂H where n+m=1 to 8; and,    -   ix) cyclic, linear, or branched perfluorocarbon and        hydrofluorocarbon amines, and ether-amines in which there are        more fluorines than hydrogens, no runs of hydrogen longer than        two (CH—CH), no —CH₂CH₃ radicals are present and no runs of        adjacent C—F bonds longer than 6 (CF—CF—CF—CF—CF—CF), and no C—H        bonds immediately adjacent to either nitrogen or oxygen; at        least until the desired concentration of said one or more        photochemically active species is achieved.

The present invention further provides for a process for forming anoptical image on a substrate, the process comprising:

-   -   a) radiating electromagnetic radiation from a source capable of        radiating electromagnetic radiation in the range of 140-260 nm;    -   b) receiving said radiation on a target disposed to receive at        least a portion of said radiation; and    -   wherein one or more optically transparent compositions is        disposed between said radiation source and said target, at least        one of said optically transparent compositions comprising a        composition treated with one or more means for extracting one or        more photochemically active species and one or more compounds        selected from the group consisting of:    -   i) cyclic, linear, or branched hydrofluorocarbons having 2 to 10        carbon atoms in which there are more fluorines than hydrogen, no        runs of adjacent C—H bonds longer than two (CH—CH), no runs of        adjacent C—F bonds longer than 8 (CF—CF—CF—CF—CF—CF), and no        —CH₂CH₃ radicals;    -   ii) X—R_(f) ^(a)[OR_(f) ^(b)]nOR_(f) ^(c) wherein X and Y can be        hydrogen or fluorine and R_(f) ^(a), R_(f) ^(b), and R_(f) ^(c)        are 1 to 3 carbon fluorocarbon radicals, linear or branched in        which there are more fluorines than hydrogens, no runs of        adjacent C—H bonds longer man two are present no —CH₂CH₃        radicals are present and no sequences with hydrogen on both        sides of an ether oxygen (CH—O—CH) are present;    -   ii) C_(n)F_(2n−v+2)H_(v) wherein n=2 to 10, v<n+1, no runs of        adjacent C—H bonds longer than two are present, no runs of        adjacent C—F bonds longer than 6 are present, and no CH₂CH₃        radicals are present;    -   iv) C_(n)F_(2n+1)CFHCFC_(m)F_(2m+1) where n equals 1 to 4; and m        equals 1 to 4;    -   v) CF₃CH₂CF₂CH₃;    -   vi) F[CF(CF₃)CF₂O]_(n)CFHCF₃ where n=1 to 5;    -   vii) F[CF(CF₃)CF₂O]_(n)CF₂CF₃ where n=1 to 5;    -   viii) HCF₂(OCF₂)_(n)(OCF₂CF₂)_(m)OCF₂H where n+m=1 to 8; and,    -   ix) cyclic, linear, or branched perfluorocarbon and        hydrofluorocarbon amines, and ether-amines in which there are        more fluorines than hydrogens, no runs of hydrogen longer than        two (CH—CH), no —CH₂CH₃ radicals are present and no runs of        adjacent C—F bonds longer than 6 (CF—CF—CF—CF—CF—F), and no C—H        bonds immediately adjacent to either nitrogen or oxygen.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the schematic layout of the apparatus employed for exposinga test specimen to 157 nm laser irradiation.

FIG. 2 shows the light path involved in the 157 nm laser irradiation ofa specimen.

FIG. 3 is a schematic drawing of the Herrick DLC liquid specimen cell,showing the annular spacers, windows and related parts.

FIG. 4 shows the relative spectral transmittance of H-Galden® ZT85 as afunction of laser irradiation dose as described In Example 4.

FIG. 5 shows the relative spectral transmittance of H-Galden® ZT85 as afunction of laser irradiation dose as described in Example 5.

FIG. 6 shows the relative spectral transmittance of H-Galden® ZT85 as afunction of laser irradiation dose as described In Example B.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to transparent fluorinated organicmaterials which have been found to be particularly well-suited foremployment in VUV photolithography. While broadly directed toapplications in the wavelength range of 140 to 280 nm, the twowavelengths of primary interest at the present state of technologicaldevelopment are at 157 nm and 193 nm. 157 nm electromagnetic radiation,by virtue of its shorter wavelength, represents a more severe conditionthan does 193 nm.

While the methods and principles taught herein are applicable totransparent fluorinated organic materials suitable for both 157 nm and193 nm photolithography, one of skill in the art will appreciate thatone or another of the specific compositions comprehended herein may bebetter suited for use at one or the other of 157 nm or 193 nmwavelengths. In the course of the discussion following hereinbelow, theterm “157 nm or 193 nm” will be used throughout to indicate that thematerials comprehended may be well suited to use at either one of thewavelengths, or may be useful at both wavelengths. Thus, for the purposeof the present invention, the term “or” should not be taken as limitingto only 157 nm or only 193 nm, but may also be taken to mean “or both”as well.

In the practice of the present invention certain compositions have beenfound to exhibit good transparency at 157 nm, 193 nm, or both. Thesecompositions comprise compounds selected from the group consisting of:

-   -   i) cyclic, linear or branched hydrofluorocarbons having 2 to 10        carbon atoms in which there are more fluorines than hydrogen, no        runs of adjacent C—H bonds longer than two (CH—CH), no runs of        adjacent C—F bonds longer than 6 (CF—CF—CF—CF—CF—CF), and no        —CH₂CH₃ radicals;    -   ii) X—R_(f) ^(a)[OR_(f) ^(b)]nOR_(f) ^(c)Y wherein X and Y can        be hydrogen or fluorine and R_(f) ^(a), R_(f) ^(b) and R_(f)        ^(c) are 1 to 3 carbon fluorocarbon radicals, linear or branched        in which there are more fluorines than hydrogens, no runs of        adjacent C—H bonds longer than two are present, and no sequences        with hydrogen on both sides of an ether oxygen (CH—O—CH) are        present;    -   iii) C_(n)F_(2n−v+2)H_(v) wherein n=2 to 10, v<n+1, no runs of        adjacent C—H bonds longer than two are present, no runs of        adjacent C—F bonds longer than 6 are present, and no CH₂CH₃        radicals are present;    -   iv) C_(n)F_(2n+1)CFHCFHC_(m)F_(2m+1) where n equals 1 to 4; and        m equals 1 to 4;    -   v) CF₃CH₂CF₂CH₃;    -   vi) F[CF(CF₃)CF₂O]_(n)CFHCF₃ where n=1 to 5;    -   vii) F[CF(CF₃)CF₂O]_(n)CF₂CF₃ where n=1 to 5;    -   viii) HCF₂(OCF₂)_(n)(OCF₂CF₂)_(m)OCF₂H where n+m=1 to 8; and,

ix) cyclic, linear, or branched perfluorocarbon and hydrofluorocarbonamines, and ether-amines in which there are more fluorines thanhydrogens, no runs of hydrogen longer than two (CH—CH), no runs ofadjacent C—F bonds longer than 6 (CF—CF—CF—CF—CF—CF), and no C—H bondsimmediately adjacent to either nitrogen or oxygen. The above compoundsare characterized by desirably low absorbance in the region from 140-260nm. Table 1 shows the measured absorbance at 157 nm for a selection ofcommercially available compounds which are comprehended among thecompositions hereinabove cited. TABLE 1 Absorbance/Micrometer (A/μm)Commercial A/μm @ Ex Name Vendor Chemical Formula 157 nm 1 Fluorinert ™3M, St. Paul, —N(CF₂CF₂CF₂CF₃)₃ 0.21 FC-40* MN 2 Vertrel ™ XF DuPont,CF₃CFHCFHCF₂CF₃ 0.0026 Fluoroproducts Wilmington, DE 5 H-Galden ®Ausimont USA, HCF₂O(CF₂O)_(n)(CF₂CF₂O)_(m)CF₂H 0.0037 ZT 85 Inc.,Thorofare, NJ 12 Solkane ™ Solvay Fluorides CF₃CH₂CF₂CH₃ 0.0025 365 mfcSt Louis, MO*Fluorinert ™ FC-40 is a mixture of perfluorinated amines of whichN(CF₂CF₂CF₂CF₃)₃ is a major component.

The transmission measurements of the fluid samples listed in Table 1were made using a Harrick Scientific Corp. (Harrick ScientificCorporation 88 Broadway Ossining, N.Y.) Demountable Liquid Cell modelDLC-M13 as shown in FIG. 3. The DLC-M13 was mounted in a VUV-Vase modelVU-302 spectroscopic ellipsometer, which is capable of performingtransmission measurements (J.A. Woolman Co., Inc. Lincoln, Nebr.). Theliquid specimen to be tested was held in a cell formed between parallelCaF2 windows by insertion of a Teflon® ring between the windows. Teflon®rings of 6 and 25 micrometer thickness were used, providing two opticalpath lengths through two aliquots of the same sample. While charging thecell, care was taken to avoid bubbles in the 8 mm diameter windowaperture.

The optical absorbance, A (μm⁻¹), per micrometer of specimen thicknessas defined in Equation 1, is defined for purposes herein as the base 10logarithm of the ratio of the transmission of the CaF₂ windows at thetest wavelength divided by the transmission at that wavelength of thetest sample (windows plus experimental specimen) divided by thethickness (t) of the test specimen—in the case of the experimentsreported herein, either 6 or 25 micrometers, as discussed hereinabove.$\begin{matrix}{{A\left( {\mu m}^{- 1} \right)} = {{A\text{/}{um}} = {\frac{{Log}_{10}\left\lfloor {T_{substrate}/T_{sample}} \right\rfloor}{t}.}}} & {{Equation}\quad 1}\end{matrix}$

To eliminate the effect of multiple reflections in the case of theliquid samples employed herein, absorbance was determined using both the6 and 25 μm cells. The spectral transmission was measured at both cellthicknesses (t₁ and t₂) and the incremental decrease in transmission (T₁and T₂) with the increase in the sample's optical path length providesthe optical absorbance/micrometer using Equation 2. $\begin{matrix}{{A\text{/}\mu\quad m} = {\frac{{\log_{10}\left( T_{1} \right)} - {\log_{10}\left( T_{2} \right)}}{t_{2} - t_{1}}.}} & {{Equation}\quad 2}\end{matrix}$

In further investigation it was found that, when irradiated by 157 nmlaser radiation at an intensity and for a duration similar to thoseexpected to be encountered in actual commercial practice, the organiccompounds suitable for the practice of the present invention in theiras-received or as-synthesized condition underwent photochemicaldarkening (PCD) and bubble formation at a rate which could limit theuseful lifetime thereof in practical commercial use. Thus, there isconsiderable incentive for finding a means for increasing the usefullifetime of organic compounds intended for use in 157 nm or 193 nmphotolithography, and for inhibiting the formation of bubbles.

One of skill in the art will appreciate that PCD and bubble formationare highly deleterious to the value in use of the transparent materialsemployed in photolithography. Photochemical instability at VUVwavelengths may be inherent in the candidate material for use in VUVphotolithography, resulting in undesirable levels of PCD and/or bubbles;this is a particular issue at the very high photon energies associatedwith 157 nm irradiation. However, one of skill in the art willappreciate that even small levels of contaminants—some of which may behighly absorbing at the wavelength of interest—may exhibit thephotochemical activity which leads to PCD and bubbles. It is thus ofconsiderable interest to determine whether extraction of potentialsources of photochemical activity may result in an improvement to PCD,bubble formation, or both.

Two particularly suspect photochemically active species at the shortwavelengths of interest herein are oxygen and moisture because of theirubiquity in nature.

Upon further investigation it is found that the preferred organiccompounds of the invention as received or as synthesized, exhibit amoisture content generally above 20 ppm and usually above 50 ppm andoften above 200 ppm; and an oxygen content generally in the range 90ppm. It is further found that when a means for extracting moisture froma liquid is applied to the organic compounds preferred for the practiceof the present invention that the moisture content is readily reduced tobelow 20 ppm, preferably below 15 ppm, more preferably below 10 ppm, andoccasionally and most preferably below 1 ppm. It is found surprisinglythat the PCD rate at 157 nm and 193 nm of the thus preparedreduced-moisture compound is reduced many fold over the startingmaterial.

It is also found that treatment of the fluorinated organic compoundssuitable for the practice of the invention with a means effective forreducing oxygen concentration is also effective in reducing PCD as wellas bubble formation.

In a preferred embodiment of the present invention, there is provided acomposition suitable for use in 157 nm or 193 nm lithography whichexhibits an extended useful lifetime by virtue of a reduced PCD rate andreduced bubble formation over the as-received fluorinated organiccompounds suitable for the practice of the present invention, saidcomposition comprising less than 20 parts per million of water, lessthan 90 ppm oxygen, and one or more compounds selected from the groupconsisting of:

-   -   i) cyclic, linear, or branched hydrofluorocarbons having 2 to 10        carbon atoms in which there are more fluorines than hydrogen, no        runs of adjacent C—H bonds longer than two (CH—CH), no runs of        adjacent C—F bonds longer than 6 (CF—CF—CF—CF—CF—CF), and no        —CH₂CH₃ radicals;    -   ii) X—R_(f) ^(a)[OR_(f) ^(b)]nOR_(f) ^(c)Y wherein X and Y can        be hydrogen or fluorine and R_(f) ^(a), R_(f) ^(b), and R_(f)        ^(c) are 1 to 3 carbon fluorocarbon radicals, linear or branched    -   in which there are more fluorines than hydrogens, no runs of        adjacent C—H bonds longer than two are present, and no sequences        with hydrogen on both sides of an ether oxygen (CH—O—CH) are        present;    -   iii) C_(n)F_(2n−v+2)H_(v) wherein n=2 to 10, v<n=1, no runs of        adjacent C—H bonds longer than two are present, no runs of        adjacent C—F bonds longer than 6 are present, and no CH₂CH₃        radicals are present;    -   iv) C_(n)F_(2n+1)CFHCFHC_(m)F_(2m+1) where n equals 1 to 4; and        m equals 1 to 4;    -   v) CF₃CH₂CF₂CH₃;    -   vi) F[CF(CF₃)CF₂O]_(n)CFHCF₃ where n=1 to 5;    -   vii) F[CF(CF₃)CF₂O]_(n)CF₂CF₃ where n=1 to 5;    -   viii) HCF₂(OCF₂)_(n)(OCF₂CF₂)_(m)OCF₂H where n+m=1 to 8; and,    -   ix) cyclic, linear, or branched perfluorocarbon and        hydrofluorocarbon amines, and ether-amines in which there are        more fluorines than hydrogens, no runs of hydrogen longer than        two (CH—CH), no runs of adjacent C—F bonds longer than 6        (CF—CF—CF—CF—CF—CF), and no C—H bonds immediately adjacent to        either nitrogen or oxygen.

Preferably the composition of the invention comprises one or morecompounds selected from the group consisting of perfluorotributylamine,perfluoro-N-methymorpholine, C_(n)F_(2n+1)CFHCFHC_(m)F_(2m+1) where nequals 1 to 4; and m equals 1 to 4 and HCF₂(OCF₂)_(n)(OCF₂CF₂)_(m)OCF₂Hwhere n+m=1 to 8, said composition having a moisture content of lessthan 20 ppm and an oxygen content of less than 90 ppm. More preferably,the composition of the invention comprises perfluorotributylamine,perfluoro-N-methymorpholine, CF₃CFHCFHCF₂CF₃, CF₃CH₂CF₂CH₃ orHCF₂O(CF₂O)_(n)(CF₂CF₂O)_(m)CF₂H where n+m=2 to 6, or a mixture thereof,said composition having a moisture content of less than 20 ppm and anoxygen content of less than 90 ppm. The organic compound of theinvention is preferably a liquid.

In another embodiment of the present invention is provided a process forthe preparation of the composition of the invention. The liquid organiccompounds preferred for the practice of the present invention arewell-known known in the art, and may be prepared according to themethods hereinabove described with reference to the published methodstherefor. In the process of the invention the liquid organic compound,or organic liquid, of the invention in its “as received” or “assynthesized” state is subject to one or more means for extractingphotochemically active species. Methods known in the art for performingextractions of particular types of contaminants are suitable for thepractice of the present invention, but care must be taken that thesemethods are executed under very clean conditions to avoid furthercontamination, thus substituting one problem for another.

In one embodiment of the process of the invention, the photochemicallyactive species is moisture. Any means for extracting moisture as isknown in the art is acceptable for the practice of the presentinvention. Suitable means include but are not limited to heating in anoven under vacuum, or under a desiccated purge gas, or both; heating ina recirculating air oven having desiccant beds; refluxing in thepresence of a desiccated purge gas, sparging with a purge gas,preferably an inert gas such as nitrogen or argon; exposing said liquidto a desiccated atmosphere at room temperature or below; contacting saidliquid with a desiccant such as molecular sieves; vaporizing said liquidand passing over a desiccant such as molecular sieves, followed bycondensation; or contacting said liquid with chemical desiccants such asisocyanates and fractionally distilling. In the case of contacting saidfluorinated organic compound with a desiccant it will normally benecessary to add a separation step upon completion of the extractionstep. One of skill in the art will appreciate that not all methods ofdrying will be suitable for every compound suitable for the practice ofthe present invention. For example, if the organic liquid is flammable,a heating method may be less desirable than some other means. Theinventors hereof do not contemplate any limitations on the methods ofdrying which may be employed to achieve the desired state of drynesswith the proviso that the method employed not introduce more undesirablecontamination than it removes, that the method not cause significantdegradation of the compound being purified, and that the method besafely executed. Thus any method known to one of skill in the art forextracting moisture from organic liquids is suitable.

Preferred for the practice of the invention is to contact said preferredorganic liquid with molecular sieves followed by filtration to separatethe thereby desiccated organic liquid from said molecular sieves. Types3A, 4A, and 5A molecular sieves are preferred because their cavities areof a size that favor the selective absorption of water from organicvapors and fluids.

In a further embodiment, the photochemically active species is oxygen.It will be understood by one of skill in the art that oxygencontamination represents an additional source of photochemicalinstability at the high energies of VUV radiation. Oxygen is of courseclosely associated with numerous degradation mechanisms in manymaterials from organics to metals. The technique of sparging with aninert gas, preferably nitrogen or argon, is found to be an effectivemeans for removing oxygen from the compositions of the invention. Othermethods suitable for removing oxygen include but are not limited toheating in an oven under vacuum, or under an oxygen free purge gas,contacting with an oxygen scavenger, repeated cycles of freezing,pulling a high vacuum and thawing, or vacuum distillation are alleffective means for extracting oxygen from the fluorinated organiccompounds suitable for use is the present invention. The inventorshereof do not contemplate any limitations on the methods of extractingoxygen which may be employed to achieve the desired oxygen concentrationwith the proviso that the method employed not introduce more undesirablecontamination than it removes, that the method not cause significantdegradation of the compound being purified, and that the method besafely executed. Thus any method known to one of skill in the art forextracting oxygen from organic liquids is suitable.

In the most preferred embodiment of the process of the invention thefluorinated organic compound is subject to extraction of photochemicallyactive species, particularly oxygen and moisture, by sparging with aninert gas such as nitrogen or argon in combination with contacting theorganic compound of the invention with molecular sieves.

Sparging is a preferred method for practicing the process of theinvention, particularly for the removal of oxygen. One method forsparging found effective in the practice of the invention is as follows:A glove box is supplied with dry, low-oxygen-content nitrogen such as99.998% or better nitrogen sold as a cylinder gas by Matheson or by theboil-off of liquid nitrogen. A liquid aliquot of about 10 ml is placedin a 20 ml glass scintillation vial. The sample is transferred into thenitrogen purged dry box. The vial is secured flat on the work surface,the plastic cap is removed from the vial, a disposable glass pipettelowered into the solvent and then nitrogen delivered via the pipettefrom the same dry, low-oxygen source as the glove box. Flow rate isadjusted to maintain vigorous bubbling of solvent short of causing thesolvent to splash out of the vial. Vigorous sparging is continued for30-60 seconds, long enough to significantly decrease oxygen content andpossibly water content without major loss of solvent to evaporation.

For the purpose of the present invention, the terms “desiccated” as in“desiccated atmosphere” or “desiccated purge gas” means simply that theatmosphere or purge gas is sufficiently low in moisture content that itcan function effectively to extract moisture from ge preferred organicliquid of the invention. Preferably, a desiccated purge gas ordesiccated atmosphere and the like will have actually been previouslysubject to an actual drying step prior to its use for extraction ofmoisture according to the present invention.

One of skill in the art will appreciate that while in a preferredembodiment, both oxygen and moisture are extracted from the fluorinatedorganic compound herein, extraction of either one but not both is alsoadvantageous. In the practice of the present invention, extraction ofany one photochemically active species will be beneficial whether or notany other photochemically active species which may be present isextracted or not. Thus, the inventors hereof contemplate embodimentswherein the moisture content is below 20 ppm, or the oxygen content isbelow 90 ppm, but wherein moisture and oxygen are not both within thedesired range of concentration. These embodiments are less preferred.

This invention further includes a process for forming an optical imageon a substrate, the process comprising:

-   -   radiating electromagnetic radiation from a source capable of        radiating electromagnetic radiation in the range of 140-260 nm;    -   receiving said radiation on a target disposed to receive at        least a portion of said radiation; and    -   wherein one or more optically transparent compositions is        disposed between said radiation source and said target, at least        one of said optically transparent compositions comprising a        composition comprising less than 20 parts per million of water,        less than 90 parts per million of oxygen, and one or more        compounds selected from the group consisting of:    -   i) cyclic, linear, or branched hydrofluorocarbons having 2 to 10        carbon atoms in which there are more fluorines than hydrogen, no        runs of adjacent C—H bonds longer than two (CH—CH), no runs of        adjacent C—F bonds longer than 6 (CF—CF—CF—CF—CF—CF), and no        —CH₂CH₃ radicals;    -   ii) X—R_(f) ^(a)[OR_(f) ^(b)]nOR_(f) ^(c)Y wherein X and Y can        be hydrogen or fluorine and R_(f) ^(a), R_(f) ^(b), and R_(f)        ^(c) are 1 to 3 carbon fluorocarbon radicals, linear or branched    -   in which there are more fluorines than hydrogens, no runs of        adjacent C—H bonds longer than two are present, and no CH₂CH₃        radicals are present;    -   and no sequences with hydrogen on both sides of an ether oxygen        (CH—O—CH) are present;    -   iii) C_(n)F_(2n−y+2)H_(v) wherein n=2 to 10, v<n+1 no runs of        adjacent C—H bonds longer than two are present, no runs of        adjacent C—F bonds longer than 6 are present, and no CH₂CH₃        radicals are present;    -   iv) C_(n)F_(2n+1)CFHCFHC_(m)F_(2m+1) where n equals 1 to 4; and        m equals 1 to 4;    -   v) CF₃CH₂CF₂CH₃;    -   vi) F[CF(CF₃)CF₂O]_(n)CFHCF₃ where n=1 to 5;    -   vii) F[CF(CF₃)CF₂O]_(n)CF₂CF₃ where n=1 to 5;    -   viii) HCF₂(OCF₂)_(n)(OCF₂CF₂)_(m)OCF₂H where n+m=1 to 8; and,

Preferably said composition disposed between said light source and saidtarget comprises one or more compounds selected from the groupconsisting of perfluorotributylamine, perfluoro-N-methymorpholine,C_(n)F_(2n+1)CFHCFHC_(m)F_(2m+1) where n equals 1 to 4; and m equals 1to 4 and HCF₂(OCF₂)_(n)(OCF₂CF₂)_(m)OCF₂H where n+m=1 to 8, saidcomposition having a moisture content of less than 20 ppm, and oxygenconcentration of less than 90 ppm. More preferably, said compositiondisposed between said light source and said target comprisesperfluorotributylamine, perfluoro-N-methymorpholine, CF₃CFHCFHCF₂CF₃,CF₃CH₂CF₂CH₃ or HCF₂O(CF₂O)_(n)(CF₂CF₂O)_(m)CF₂H where n+m=2 to 6, or amixture thereof, said composition having a moisture content of less than20 ppm. The organic compound of the invention is preferably a liquid.

It is expected that linear perfluoropolyethers of the structure X—R_(f)^(a)[OR_(f) ^(b)]_(n)OR_(f) ^(c)Y will show high durability to UVradiation as molecular weights increase, the upper practical limitlikely being inconveniently high viscosity. This would includeF[CF(CF₃)CF₂O]CFHCF₃ up to n=−100, F[CF(CF)₃CF₂O]_(n)CF₂CF₃ up ton=−100, HCF₂(OCF₂)_(n)(OCF₂CF₂)_(m)OCF₂H up to n+m=−100, andFCF₂(OCF₂)_(n)(OCF₂CF₂)_(m)OCF₂F up to n+m=−100.

In one embodiment of the photolithographic process of the invention, 157nm radiation from a F₂ excimer laser transmitted through a photomask,typically comprising a chrome metal circuit patterned on glass byelectron beam imaging forms an image of the circuit pattern on aphotoresist. Various materials for photoresist compositions have beendescribed in Introduction to Microlithography, Second Editon by L. F.Thompson. C. G. Willson, and M. J. Bowden, American Chemical Society,Washington, D.C., 1994.

The composition of the present invention may be employed in any numberof ways which will cause it to become disposed between the light sourceand the target. Certain organic fluids are employed as solvents for thepolymers in spin-coating operations. A solvent may serve to plasticize apolymeric film. A solvent may be employed in an adhesive formulation.Or, in a preferred embodiment of the invention herein, an organic fluidor gel may be employed as an immersion medium in immersionphotolithography, as disclosed hereinabove. But, whether a polymer or alow molecular weight organic composition, if the composition resides inthe light path between the source and the target, the composition needsto be transparent and durable.

In one preferred embodiment of the present invention the compositions ofthe invention are present in a pellicle employed in 157 nmphotolithography. In a second preferred embodiment of the presentinvention, the compositions of the invention are present in a pellicleemployed in 193 nm photolithography. A pellicle is a free standingpolymer film, typically 0.8 micrometers in thickness which is placedover a photomask or other template pattern to keep particulatecontamination out of the photomask object plane in order to reduce thedefect level in the resulting image. The pellicle film must have hightransparency at the lithographic wavelength for image formation and mustexhibit a reasonable lifetime under repeated exposures to thelithographic irradiation. The term “reasonable” is of course a relativeterm determined by the economics of the particular application.

Fluorocarbon polymers are preferred for use in forming pellicles for useat VUV wavelengths. One method by which pellicles may be fabricated isby spin-coating from solution according to methods well-known in theart. As spun, the pellicle film may contain up to 10 wt % residualsolvent which is not readily removed and may even be desirable in orderto provide some plasticization to the film. It will be appreciated byone of skill in the art that a relatively small concentration of asolvent which lacks transparency at the lithographic wavelength may havea catastrophic effect on the transparency of the pellicle. Similarly, ifthe residual solvent exhibits photochemical instability, the durabilityof the pellicle film will be reduced. The compositions of the presentinvention exhibit a combination of high transparency and high radiationdurability which makes them particularly useful as solvents for thepreparation of pellicles for use in 157 nm or 193 nm photolithography.

Similar considerations and benefits will accrue to the employment of thecompositions of the invention as solvents in the preparation of aphotoresist layer by spin coating. The reason for this is that residualsolvent is always left behind when spin coating resist films. If thisresidual solvent absorbs light strongly, light absorbtion at the top andbottom of the resist film become unequal enough to result in poorpattern development. Furthermore, if the residual solvent isphotochemically unstable, the photoresist layer may exhibit defects uponexposure to VUV radiation. The fluids of this invention are highlyattractive spin coating solvents because they will not noticeablyincrease absorption in photoresist layers when left behind as a residue.

In a further preferred embodiment, the composition of the presentinvention is employed in immersion photolithography as described bySwitkes et al, op. cit. In immersion photolithography at least eitherthe source or the target is immersed in the optically transparentcomposition of the invention. Preferably, both source and target aretherein immersed. Among the requirements for the immersion medium thatSwitkes discusses are that it be transparent enough to allow a workingdistance of 10's of micrometers and that it have high radiationdurability under 157 nm or 193 nm irradiation. The combination of hightransparency and high radiation durability of the compositions of thepresent invention makes them particularly well-suited for immersionlithography applications at 157 nm or 193 nm wavelengths.

In still further embodiments, the compositions of the present inventionare useful in the fabrication of sheets, layers, coatings, and filmsused in lenses, light guides, anti-reflective coatings and layers,windows, protective coatings, and glues suitable for use in 157 nm or193 nm photolithography.

The compositions of the present invention are particularly useful in theformation of anti-reflection coatings and optical adhesives by virtue oflow absorbance at 157 nm or 193 nm. The composition of the invention canbe used to reduce the light reflected from the surface of a transparentsubstrate of a relatively higher index of refraction. This decrease inthe reflected light, leads to a concomitant increase, in the lighttransmitted through the transparent substrate material.

The compositions of the present invention are useful in the manufactureof transmissive optical elements, such as lenses and beam splitters, foruse in the vacuum UV region.

These compositions may also be used as elements in a compound lensdesigned to reduce chromatic aberrations. At present only CaF₂ andpossibly hydroxyl free silica are viewed as having sufficienttransparency at 157 nm or 193 nm to be used in transmissive focussingelements. It is also commonly known (e.g, see R. Kingslake, AcademicPress, Inc., 1978, Lens Design Fundamentals, p. 77) that by using asecond material of different refractive index and dispersion, anachromatic lens can be created. By using the composition of the presentinvention in conjunction with CaF₂, it is expected that an achromaticlens can be constructed from this and other similar materials describedin this application.

The extraction methods herein described, particularly for moisture andoxygen, are particularly useful for preparing fluorinated organicliquids for use in immersion lithography. The extraction methods hereintaught are not limited to the specific compositions herein disclosed,but may be applied with excellent results to any fluorinated organicliquid contemplated for use as the immersion medium for immersionlithography in the VUV. Thus, even less preferred fluorinated organiccompositions than those specifically disclosed herein, such as thoseexhibiting absorbance/micrometer up to 5, will exhibit improvements inPCD and bubble formation when extracted according to the processhereinabove described. By application of the methods herein, themoisture content of any such liquid contemplated can be reduced to below20 ppm, and the oxygen content to below 90 ppm.

It is found in the practice of the present invention that in some casesthe measured PCD rate is dependent upon the dose received, with thehighest rate being recorded for low initial doses. It is further foundin the practice of the invention that PCD does not proceed indefinitelyuntil the transparency has virtually disappeared. In some cases insteaddarkening occurs at a decreasing rate with increasing dose until anasymptote still at high transmission levels is approached and no furtherdarkening is observed with increasing dose. It is further found in thepractice of the invention that at least in certain cases, a cessation ofexposure to 157 nm irradiation after the asymptotic level is reachedresults in further darkening. However, upon re-exposure to 157 nmradiation the degree of darkening is actually reduced and again theasymptotic level of transparency is re-achieved.

These phenomena are illustrated in certain specific embodiments of theinvention hereinbelow.

The present invention is further described but not limited to thefollowing specific embodiments.

EXAMPLES

For the purpose of the examples hereinbelow, the absorbance of a testspecimen is determined prior to laser irradiation, and then again afterlaser irradiation at 157 nm, using the methods and equipment describedhereinabove with the exception that only the 6 μm or 25 μm cell wasused, as specified in Tables 2 and 3. The dose of 157 nm radiation isdetermined according to the power output of the laser and the durationof the exposure. The difference between the two absorption readings isdivided by the dosage received to give a parameter defined for thepurposes herein to be the linear PCD rate. For the purpose of comparingone specimen to another, the linear PCD rate is then employed. This isreferred to herein as the “10% PCD” dosage.

To calculate the PCD rate, we calculate the induced absorbance/umdivided by the given irradiation dose (D). These are calculated fromEquation 3 where T₁ is the initial transmission for a cell of thicknesst and T₂ is the final transmission after a dose D. $\begin{matrix}{{A_{i}/D} = {\frac{{\log_{10}\left( T_{1} \right)} - {\log_{10}\left( T_{2} \right)}}{t}/{D.}}} & {{Equation}\quad 3}\end{matrix}$

The 10% PCD Lifetime, in units of Joules/cm² dose of 157 nm radiation iscalculated from the ratio of the induced absorption necessary to producea transmission drop, ΔT, of 10% for a sample of thickness t=0.8micrometers, as given by Equation 4. An increase in the 10% PCD lifetimecorresponds to increased radiation durability. $\begin{matrix}{{Lifetime} = {\frac{A_{i}}{{PCD}\quad{rate}} = {\frac{{Log}_{10}\left( {T_{init}/\left( {T_{inir} - {\Delta\quad T}} \right)} \right)}{t\quad{PCD}\quad{rate}}.}}} & {{Equation}\quad 4}\end{matrix}$

Water concentration was determined according to the Karl Fischer methodcommonly employed in the art. The effect of drying over molecular sievesof the preferred compositions of the invention is indicated in Table 4.

Laser irradiation at 157 nm was accomplished inside a nitrogen purgeddry-box using an Optex F₂ excimer laser made by Lambda Physik (LambdaPhysik USA, Inc, Fort Lauderdale, Fla.). In practice the DCL cellhereinabove described was simply moved from the ellipsometer describedhereinabove to a holder in the dry box putting the test sample into thepath of the laser. The laser pulse rate was 50 hz, putting out 1mJ/cm²/pulse energy density or 3 Joules/cm²/minute. All doses reportedhere are Joules per cm² area irradiated. The reported doses arecorrected for the losses associated with the CaF₂ windows so that thedoses represent the actual dose incident upon the sample itself, not thetotal dose incident upon the measurement cell.

As in all experimental measurements, the accuracy of the measured valuesis a function of the sample and measurement apparatus. The inherentsensitivity of spectral transmission and absorbance measurements isaffected by the optical path length of the sample, and the transmissiondrop that occurs as light transmits through the sample in themeasurement. As the transmission drop decreases, the accuracy of theabsorbance measurement decreases. A transmission difference of ˜0.1% isnear the limit of the measurement method. In such a case, a thickersample, with a longer path length, is required to keep the measuredtransmission drop larger than the instrument's sensitivity. TABLE 2 10%PCD Lifetime and moisture content of as-received organic compoundsMoisture 10% PCD Content (as Thickness Initial Dose Life-time received)Ex. Solvent um (J/cm²) (J/cm²) ppm Comp. Ex. 2 CF₃CFHCFHCF₂CF₃ 6 3  9.972 Vertrel ™ XF Comp. Ex. 3 CF₃CFHCFHCF₂CF₃ 6 6 52.7 72 Vertrel ™ XFComp. Ex. 4 CF₃CFHCFHCF₂CF₃ 6 20 47.5 72 Vertrel ™ XF Comp. Ex. 5HCF₂O(CF₂O)_(n) 25 15 Bubble 257 (CF₂CF₂O)_(m)CF₂H H-Galden ® ZT 85Comp. Ex. 6 HCF₂O(CF₂O)_(n) 25 30 Bubble 257 (CF₂CF₂O)_(m)CF₂HH-Galden ® ZT 85 Comp. Ex. 7 HCF₂O(CF₂O)_(n) 25 15 Bubble 257(CF₂CF₂O)_(m)CF₂H H-Galden ® ZT 85

For the purpose of the present invention, the experimental comparisonsmade herein were determined for the initial PCD rate measured in eachparticular case. The initial dosage was not always the same. TABLE 3 10%PCD Lifetimes of Treated Samples 10% PCD Thick- Life- Water ness Pre-Dose time Content Ex. Solvent um treatment (J/cm²) (J/cm²) (ppm) 1Vertrel ™ XF 6 Sparge  6 128.2 0.71 2 Vertrel ™ XF 6 Sparge 20 200.40.71 3 H-Galden ® 25 Sparge  6J 497 0.94 ZT 85 4 H-Galden ® 25 Mol. 12.5457 0.94 ZT 85 Sieve 5 H-Galden ® 25 Mol. 25.4 868 0.94 ZT 85 Sieve 6H-Galden ® 25 Mol. 12.75J 569 0.94 ZT 85 Sieve

TABLE 4 Effect of Drying over 3A Molecular Sieves PPM H₂O Ex. #Description As received Dried 7 H-Galden ® 257 0.94 8 Solkane ™ 365 mfc218 12 9 Vertrel ™ XF 72 0.71

Comparative Example 1

Liquid sample cells having CaF₂ windows spaced 6 μm and 25 μm apart wereused. Transmitted light intensities were measured with the cells emptyand with the cells filled with ˜N(CF₂CF₂CF₂CF₃)₃, Fluorinert™ FC-40.˜N(CF₂CF₂CF₂CF₃)₃, Fluorinert™ FC-40 was found have A/μm=0.21 at 157 nm.

A sample of FC-40 as received was loaded into a liquid sample cell with6 micrometer spacers, and then irradiated with 1.1 Joules/cm² of 157 nmradiation. This material had a 10% PCD lifetime of <0.2 Joules/cm².

Comparative Example 2

Liquid sample cells having CaF₂ windows spaced 6 μm and 25 μm part wereused. Transmitted light intensities were measured with the cells filledwith Vertrel® XF. Vertrel® XF was found have A/μm=0.0026 at 157 nm.

A sample of Vertrel® XF as received was loaded into a liquid sample cellwith 6 micrometer spacers, and then irradiated with 3 Joules/cm² of 157nm radiation. This sample showed a 10% PCD lifetime of 9.9 Joules/cm².

Comparative Example 3 and Example 1

A sample of Vertrel® XF as received was loaded into a liquid sample cellwith 6 micrometer spacers, and then irradiated with 6 Joules/cm² of 157nm radiation. This sample showed a 10% PCD lifetime of 52.7 Joules/cm².

A sample of Vertrel® XF which was vigorously sparged for 1 minute wasloaded into a liquid sample cell with 6 micrometer spacers, and thenirradiated with 6 Joules/cm² of 157 nm radiation. This sample showed a10% PCD lifetime of 128.2 Joules/cm².

Comparative Example 4 and Example 2

A sample of Vertrel® XF as received was loaded into a liquid sample cellwith 6 micrometer spacers, and then irradiated with 20 Joules/cm² of 157nm radiation. This sample showed a 10% PCD lifetime of 47.5 Joules/cm².

A sample of Vertrel® XF which was vigorously sparged for 1 minute wasloaded into a liquid sample cell with 6 micrometer spacers, and thenirradiated with 20 Joules/cm² of 157 nm radiation. This sample showed a10% PCD lifetime of 200.4 Joules/cm².

Example 3

Liquid sample cells having CaF₂ windows spaced 6 micrometer and 25micrometer apart were used. Transmitted light intensities were measuredwith the cells filled with H-Galden® ZT 85. H-Galden® ZT 85 was foundhave A/μm=0.0037 at 157 nm.

A sample of H-Galden® ZT 85 which was vigorously sparged for 1 minutewas loaded into a liquid sample cell with 25 micrometer spacers, andthen irradiated with 6 Joules/cm² of 157 nm radiation. This sampleshowed a 10% PCD lifetime of 497 Joules/cm².

Comparative Example 5

A sample of H-Galden® ZT 85 as received was loaded into a liquid samplecell with 25 micrometer spacers, and then irradiated with 15 Joules/cm²of 157 nm radiation. Bubbles formed in the liquid cell.

Comparative Example 6

A sample of H-Galden® ZT 85 as received was loaded into a liquid samplecell with 25 micrometer spacers, and then irradiated with 30 Joules/cm²of 157 nm radiation. Bubbles formed in the liquid cell.

Comparative Example 7

A sample of H-Galden® ZT 85 with no pretreatment was loaded into aliquid sample cell with 25 micrometer spacers, and then irradiated with30 Joules/cm² of 157 nm radiation. Bubbles formed in the liquid cell.

Example 4

A Hastelloy tube about two feet long by 1 inch in diameter was loadedwith 3A molecular sieves, placed in a 310° C. tube oven, and purged withnitrogen gas overnight. The next morning the nitrogen purge gas wasfirst passed through a liquid nitrogen chilled trap to make sure it wasreasonably dry for the remainder of the experiment. The tube furnace wasthen turned off and the molecular sieves allowed to return to roomtemperature while maintaining the purge of dry nitrogen. About 1-2 gramsof dry 3A molecular sieves were poured directly out the back end of theHastelloy tube into a one ounce sample vial already containing 10 ml ofH-Galden® ZT 85 solvent. The vial was immediately capped with a rubberseptum and then rolled overnight to make sure of good contact betweenthe solvent and the 3A molecular sieves.

The H-Galden® ZT 85 sample was filtered using a 0.45 micron glasssyringe filter. A sample of thus treated H-Galden® ZT 85 was loaded intoa liquid sample cell with 25 micrometer spacers, and then irradiatedwith 157 nm radiation. The irradiation was done in an initial dose of12.5 Joules/cm² followed by a final dose of 36 Joules/cm², to produce atotal dose of 48.5 Joules/cm². The 10% PCD lifetime over the initialdose was 457 Joules/cm².

The relative transmission to dose for is shown in FIG. 4. Pyroelectricdetectors (Scientech PHF-25, Scientech, Inc. Boulder, Colo.) and a powermeter/ratiometer (Scientech model Vector D200) which were built in tothe laser irradiation set-up as shown in FIG. 1, were used to measurethe in situ variation of the relative sample transmission withincreasing laser radiation dose. FIG. 4, shows a rapid decrease in thetransmission during the initial 12.5 Joule dose. After the initial dosethe sample had been removed at point M for a spectroscopic measurementand then replaced in the laser irradiation apparatus for administrationof the subsequent irradiation dose.

The large initial transient in the photochemical darkening, which thenstabilizes beyond a certain dose as shown by the relative transmissionto dose in FIG. 4 demonstrated that for applications which requirestability in the transmission over long doses, for example immersionlithography or a liquid pellicle, then preconditioning of the materialdirectly prior to use may produce very long and stable transparency.

Example 5

The methods of Example 4 were repeated again using H-Galden® ZT85. Thelaser irradiation was done in an initial dose of 25.4 Joules/cm²followed by a final dose of 87.5 Joules/cm², to produce a total dose of113 Joules/cm². The 10% PCD lifetime over the initial 25.4 Joule dosewas 868 Joule s/cm².

The relative transmission to dose was determined as in Example 4 and isshown in FIG. 5 where M represents the same interruption in irradiation.The relative transmission to dose during the final 87.5 Joule dose wasnearly constant.

Example 6

The methods and materials of Example 4 were repeated to prepare aspecimen of H-Galden® ZT85 for testing. The irradiation was done in aninitial dose of 12.75 Joules/cm² followed by a final dose of 12.25Joules/cm², to produce a total dose of 25 Joules/cm². The 10% PCDlifetime over the initial 12.75 Joule dose was 569 Joules/cm².

The relative transmission to dose is shown in FIG. 6. M represents thesame relatively short interruption of irradiation as in FIGS. 4 and 5.TD represents an interruption of 16 hours between the initial and finaldoses.

Example 7

A one ounce sample vial was loaded with 10 ml of H-Galden® ZT 85 solventand immediately capped with a rubber septum. Karl Fisher analysis ofthis H-Galden® ZT 85 found 257 ppm of water. H-Galden® ZT 85 as suppliedby the vendor and as handled in ordinary glassware under ordinarylaboratory conditions can be thus be expected to contain about 257 ppmof water.

A Hastelloy tube about two foot long by 1 inch in diameter was loadedwith 3A molecular sieves, placed in a 310° C. tube oven, and purged withnitrogen gas overnight. The next morning the nitrogen purge gas wasfirst passed through a liquid nitrogen chilled trap to make sure it wasreasonably dry for the remainder of the experiment. The tube furnace wasthen turned off and the molecular sieves allowed to return to roomtemperature while maintaining the purge of dry nitrogen. About 1-2 gramsof dry 3A molecular sieves were poured directly out the back and of theHastelloy tube into a one ounce sample vial already containing 10 ml ofH-Galden® ZT 85 solvent. The vial was immediately capped with a rubberseptum and then rolled overnight to male sure of good contact betweenthe solvent and the 3A molecular sieves. A sample syringed out for KarlFisher analysis analyzed for 0.94 ppm water.

Example 8

A one ounce sample vial was loaded with 10 ml of Solkane™ 365 mfcsolvent and immediately capped with a rubber septum. Karl Fisheranalysis of this Solkane™ 365 mfc found 218 ppm of water. Solkane™ 365mfc as supplied by the vendor and as handled in ordinary glassware underordinary laboratory conditions can be thus be expected to contain about218 ppm of water.

A Hastelloy tube about two foot long by 1 inch in diameter was loadedwith 3 A molecular sieves, placed in a 310° C. tube oven, and purgedwith nitrogen gas overnight. The next morning the nitrogen purge gas wasfirst passed through a liquid nitrogen chilled trap to make sure it wasreasonably dry for the remainder of the experiment. The tube furnace wasthen turned off and the molecular sieves allowed to return to roomtemperature while maintaining the purge of dry nitrogen. About 1-2 gramsof dry 3 A molecular sieves were poured directly out the back end of theHastelloy tube into a one ounce sample vial already containing 10 ml ofSolkane™ 365 mfc solvent. The vial was immediately capped with a rubberseptum and then rolled overnight to make sure of good contact betweenthe solvent and the 3 A molecular sieves. A sample syringed out for KarlFisher analysis analyzed for 12 ppm water.

Example 9

A one ounce sample vial was loaded with 10 ml of Vertrel™ XF solvent andimmediately capped with a rubber septum. Karl Fisher analysis of thisVertrel™ XF found 72 ppm of water. Vertrel™ XF as supplied by the vendorand as handled in ordinary glassware under ordinary laboratoryconditions can be thus be expected to contain about 72 ppm of water.

A Hastelloy tube about two foot long by 1 inch in diameter was loadedwith 3A molecular sieves, placed in a 310° C. tube oven, and purged withnitrogen gas overnight. The next morning the nitrogen purge gas wasfirst passed through a liquid nitrogen chilled trap to make sure it wasreasonably dry for the remainder of the experiment. The tube furnace wasthen turned off and the molecular sieves allowed to return to roomtemperature while maintaining the purge of dry nitrogen. About 1-2 gramsof dry 3 A molecular sieves were poured directly out the back end of theHastelloy tube into a one ounce sample vial already containing 10 ml ofVertrel™ XF solvent. The vial was immediately capped with a rubberseptum and then rolled overnight to make sure of good contact betweenthe solvent and the 3 A molecular sieves. A sample syringed out for KarlFisher analysis analyzed for 0.71 ppm water.

1. An organic composition comprising less than 20 parts per million ofwater, less than 90 ppm of oxygen, and one or more compounds selectedfrom the group consisting of: i) cyclic, linear, or branchedhydrofluorocarbons having 2 to 10 carbon atoms in which there are morefluorines than hydrogen, no runs of adjacent C—H bonds longer than two(CH—CH), no runs of adjacent C—F bonds longer than 6(CF—CF—CF—CF—CF—CF), and no —CH₂CH₃ radicals; ii) X—R_(f) ^(a)[OR_(f)^(b)]nOR_(f) ^(c)Y wherein X and Y can be hydrogen or fluorine and R_(f)^(a), R_(f) ^(b), and R_(f) ^(c) are 1 to 3 carbon fluorocarbonradicals, linear or branched in which there are more fluorines thanhydrogens, no runs of adjacent C—H bonds longer than two are present, no—CH₂CH₃ radicals are present and no sequences with hydrogen on bothsides of an ether oxygen (CH—O—CH) are present; iii)C_(n)F_(2n−v+2)H_(v) wherein n=2 to 10, v<n+1, the number of fluorinesequals or exceeds the number of hydrogens, no runs of adjacent C—H bondslonger than two are present, no runs of adjacent C—F bonds longer than 6are present, and no CH₂CH₃ radicals are present; iv)C_(n)F_(2n+1)CFHCFHC_(m)F_(2m+1) where n equals 1 to 4; and m equals 1to 4; v) CF₃CH₂CF₂CH₃; vi) F[CF(CF₃)CF₂O]_(n)CFHCF₃ where n=1 to 5; vii)F[CF(CF₃)CF₂O]_(n)CF₂CF₃ where n 1 to 5; viii)HCF₂(OCF₂)_(n)(OCF₂CF₂)_(m)OCF₂H where n+m=1 to 8; and, ix) cyclic,linear, or branched perfluorocarbon and hydrofluorocarbon amines, andether-amines in which there are more fluorines than hydrogens, no runsof hydrogen longer than two (CH—CH), no —CH₂CH₃ radicals are present, noruns of adjacent C—F bonds longer than 6 (CF—CF—CF—CF—CF—CF), and no C—Hbonds immediately adjacent to either nitrogen or oxygen.
 2. Thecomposition of claim 1 wherein said one or more compounds are selectedfrom the group consisting of perfluorotributylamine,perfluoro-N-methymorpholine, C_(n)F_(2n+1)CFHCFHC_(m)F_(2m+1) where nequals 1 to 4; and m equals 1 to 4 and HCF₂(OCF₂)_(n)(OCF₂CF₂)_(m)OCF₂Hwhere n+m=1 to
 8. 3. The composition of claim 1 wherein said one or morecompounds are selected from the group consisting ofperfluorotributylamine, perfluoro-N-methymorpholine, CF₃CFHCFHCF₂CF₃,CF₃CH₂CF₂CH₃ and HCF₂O(CF₂O)_(n)(CF₂CF₂O)_(m)CF₂H where n+m=2 to
 6. 4.The composition of claim 1 wherein at least one of said one or morecompounds is a liquid.
 5. A process for preparing an organic compositionfor use in optical imaging applications comprising subjecting totreatment with one or more means for extracting one or morephotochemically active species, a compound selected from the groupconsisting of: i) cyclic, linear, or branched hydrofluorocarbons having2 to 10 carbon atoms in which there are more fluorines than hydrogen, noruns of adjacent C—H bonds longer than two (CH—CH), no runs of adjacentC—F bonds longer than 6 (CF—CF—CF—CF—CF—CF), and no —CH₂CH₃ radicals;ii) X—R_(f) ^(a)[OR_(f) ^(b)]nOR_(f) ^(c)Y wherein X and Y can behydrogen or fluorine and R_(f) ^(a), R_(f) ^(b), and R_(f) ^(c) are 1 to3 carbon fluorocarbon radicals, linear or branched in which there aremore fluorines than hydrogens, no runs of adjacent C—H bonds longer thantwo are present, no —CH₂CH₃ radicals are present and no sequences withhydrogen on both sides of an ether oxygen (CH—O—CH) are present; iii)C_(n)F_(2n−v+2)H_(v) wherein n=2 to 10, v<n+1, no runs of adjacent C—Hbonds longer than two are present, no runs of adjacent C—F bonds longerthan 6 are present, and no CH₂CH₃ radicals are present; iv)C_(n)F_(2n+1)CFHCFHC_(m)F_(2m+1) where n equals 1 to 4; and m equals 1to 4; v) CF₃CH₂CF₂CH₃; vi) F[CF(CF₃)CF₂O]_(n)CFHCF₃ where n=1 to 5; vii)F[CF(CF₃)CF₂O]_(n)CF₂CF₃ where n=1 to 5; viii)HCF₂(OCF₂)_(n)(OCF₂CF₂)_(m)OCF₂H where n+m=1 to 8; and, ix) cyclic,linear, or branched perfluorocarbon and hydrofluorocarbon amines, andether-amines in which there are more fluorines than hydrogens, no runsof hydrogen longer than two (CH—CH), no —CH₂CH₃ radicals are present andno runs of adjacent C—F bonds longer than 6 (CF—CF—CF—CF—CF—CF), and noC—H bonds immediately adjacent to either nitrogen or oxygen; at leastuntil the desired concentration of said one or more photochemicallyactive species is achieved.
 6. The process of claim 5 wherein said oneor more photochemically active species comprises moisture, and thedesired concentration is below 20 parts per million.
 7. The process ofclaim 5 wherein said one or more photochemically active speciescomprises oxygen, and the desired concentration is below 90 parts permillion.
 8. The process of claim 5 wherein said one or morephotochemically active species comprises moisture and oxygen and thedesired concentrations are below 20 parts per million and below 90 partsper million, respectively.
 9. The process of claim 5 wherein said one ormore compounds are selected from the group consisting ofperfluorotributylamine, perfluoro-N-methymorpholine,C_(n)F_(2n+1)CFHCFHC_(m)F_(2m+1) where n equals 1 to 4; and m equals 1to 4 and HCF₂(OCF₂)_(n)(OCF₂CF₂)_(m)OCF₂H where n+m=1 to
 8. 10. Theprocess of claim 5 wherein said one or more compounds are selected fromthe group consisting of perfluorotributylamine,perfluoro-N-methymorpholine, CF₃CFHCFHCF₂CF₃, CF₃CH₂CF₂CH₃ andHCF₂O(CF₂O)_(n)(CF₂CF₂O)_(m)CF₂H where n+m=2 to
 6. 11. The process of Ca5 wherein at least one of said one or more compounds is a liquid. 12.The process of claim 5 wherein said means comprises contacting saidcompound with molecular sieves.
 13. The process of claim 5 wherein saidmeans comprises sparging with an inert gas.
 14. The process of claim 5wherein said means comprises contacting said compound with molecularsieves and sparging said compound with an inert gas.
 15. A process forforming an optical image on a substrate, the process comprising: a)radiating electromagnetic radiation from a source capable of radiatingelectromagnetic radiation in the range of 140-260 nm; b) receiving saidradiation on a target disposed to receive at least a portion of saidradiation; and wherein one or more optically transparent compositions isdisposed between said radiation source and said target, at least one ofsaid optically transparent compositions comprising a composition treatedwith one or more means for extracting one or more photochemically activespecies and one or more compounds selected from the group consisting of:i) cyclic, linear, or branched hydrofluorocarbons having 2 to 10 carbonatoms in which there are more fluorines than hydrogen, no runs ofadjacent C—H bonds longer than two (CH—CH), no runs of adjacent C—Fbonds longer than 6 (CF—CF—CF—CF—CF—CF), and no —CH₂CH₃ radicals; ii)X—R_(f) ^(a)[OR_(f) ^(b)]nOR_(f) ^(c)Y wherein X and Y can be hydrogenor fluorine and R_(f) ^(a), R_(f) ^(b) and R_(f) ^(c) are 1 to 3 carbonfluorocarbon radicals, linear or branched in which there are morefluorines than hydrogens, no runs of adjacent C—H bonds longer than twoare present, no —CH₂CH₃ radicals are present and no sequences withhydrogen on both sides of an ether oxygen (CH—O—CH) are present; iii)C_(n)F_(2n+2)H_(v) wherein n=2 to 10, v<n+1, no runs of adjacent C—Hbonds longer than two are present, no runs of adjacent C—F bonds longerthan 6 are present, and no CH₂CH₃ radicals are present; iv)C_(n)F_(2n+1)CFHCFHC_(m)F_(2m+1) where n equals 1 to 4; and m equals 1to 4; v) CF₃CH₂CF₂CH₃; vi) F[CF(CF₃)CF₂O]_(n)CFHCF₃ where n=1 to 5; vii)F[CF(CF₃)CF₂O]_(n)CF₂CF₃ where n=1 to 5; viii)HCF₂(OCF₂)_(n)(OCF₂CF₂)_(m)OCF₂H where n+m 1 to 8; and, ix) cyclic,linear, or branched perfluorocarbon and hydrofluorocarbon amines, andether-amines in which there are more fluorines than hydrogens, no runsof hydrogen longer than two (CH—CH), no —CH₂CH₃ radicals are present andno runs of adjacent C—F bonds longer than 6 (CF—CF—CF—CF—CF—CF), and noC—H bonds immediately adjacent to either nitrogen or oxygen.
 16. Theprocess of claim 15 wherein said one or more compounds are selected fromthe group consisting of perfluorotributylamine,perfluoro-N-methymorpholine, C_(n)F_(2n+1)CFHCFHC_(m)F_(2m+1) where nequals 1 to 4; and m equals 1 to 4 and HCF₂(OCF₂)_(n)(OCF₂CF)_(m)OCF₂Hwhere n+m=1 to
 8. 17. The process of claim 15 wherein said one or morecompounds are selected from the group consisting ofperfluorotributylamine, perfluoro-N-methymorpholine, CF₃CFHCFHCF₂CF₃,CF₃CH₂CF₂CH₃ and HCF₂O(CF₂O)_(n)(CF₂CF₂O)_(m)CF₂H where n+m=2 to
 6. 18.The process of claim 15 wherein at least one of said one or morecompounds is a liquid.
 19. The process of claim 15 wherein said at leastone of said radiation source and said target are immersed in saidoptically transparent composition.
 20. The process of claim 15 whereinboth radiation source and target are immersed in said opticallytransparent composition.
 21. The process of claim 15 wherein saidtreated composition comprises less than 20 parts per million of water,less than 90 parts per million of oxygen.
 22. The process of claim 15wherein said means comprises contacting said compound with molecularsieves.
 23. The process of claim 15 wherein said means comprisessparging with an inert gas.
 24. The process of claim 15 wherein saidmeans comprises contacting said compound with molecular sieves andsparging said compound with an inert gas.